1. Field of the Invention
This invention relates to a cone-pin type blocking synchronizer for a multiple speed manual transmission More particularly, the invention pertains to such a synchronizer having multiple conical friction elements for synchronizing the speeds of a shaft and a gear wheel before clutch engagement.
2. Description of the Prior Art
Automotive manual transmissions currently use synchronizing clutches to make gear changes. These synchronizing clutches usually employ frictional engagement between the synchronizer and the gear to be engaged when the speeds of these components are asynchronous, the frictional connection continuing until synchronization occurs. After the speeds are made synchronous, the components are driveably connected through positive mechanical means.
Usually the frictional engagement is made when a conical friction surface is forced by the vehicle operator into contact with a complimentary conical friction surface fixed to one of the gear wheels. The gear wheel is connected through the synchronizer to the shaft on which it is journalled after synchronization by moving spline teeth on the clutch sleeve into engagement with clutching teeth on the gear wheel.
High torque capacity engines require large neutral clutches whose components, which have large polar moments of inertia, are fixed to the engine shaft and input shaft of the transmission. When gear shifts are made, the rotating inertia of these components requires that a large torque be applied to the gear wheel while its speed is synchronized with that of the output shaft or the countershaft of the transmission and before a mechanical connection is made by the synchronizing clutch. This inertial torque must be accomodated in the synchronizing clutch in a relatively small space provided between the gear wheels on the shaft to which the synchronizer driveably connects the gear wheels. Large vehicles, particularly heavily loaded trucks, tractors and the like, require that gear changes be made rapidly and with the least possible change in engine speed and vehicle speed in order to conserve the kinetic energy of the vehicle, particularly when climbing hills. The synchronizing clutches in the prior art require large friction surfaces, which require a large space for the synchronizer clutch in order to meet the torque capacity requirements of the clutch. In vehicles equipped with prior art synchronizers, the vehicle operator must apply a large force to the gear shift lever when making gear changes so that gear shifts are made rapidly. Alternatively, if less shifting force is applied, the period for gear engagement is protracted, and the kinetic energy of the vehicle is dissipated.